R-410A Overview
R-410A (sold as Puron° by Carrier) has been the dominant residential refrigerant since replacing R-22 in the mid-2000s. It operates at significantly higher pressures than R-22, requires POE (polyolester) oil, and cannot be used in equipment designed for R-22. Production of R-410A is being phased down under AIM Act regulations, with R-454B (Puron Advance) replacing it in new equipment.
Critical safety note: R-410A cylinder pressure can exceed 250 PSI at room temperature. Always use manifold gauges and equipment rated for R-410A (800 PSI working pressure minimum).
R-410A Pressure/Temperature Chart
| Temp °F | Temp °C | Pressure (PSIG) |
|---|---|---|
| -20 | -29 | 23.5 |
| -10 | -23 | 36.5 |
| 0 | -18 | 52.0 |
| 10 | -12 | 70.5 |
| 20 | -7 | 92.5 |
| 30 | -1 | 118.2 |
| 32 | 0 | 122.3 |
| 40 | 4 | 147.8 |
| 50 | 10 | 182.5 |
| 55 | 13 | 202.0 |
| 60 | 16 | 222.9 |
| 65 | 18 | 245.4 |
| 70 | 21 | 269.6 |
| 75 | 24 | 295.5 |
| 80 | 27 | 323.3 |
| 85 | 29 | 353.0 |
| 90 | 32 | 384.7 |
| 95 | 35 | 418.5 |
| 100 | 38 | 454.5 |
| 105 | 41 | 492.8 |
| 110 | 43 | 533.5 |
| 115 | 46 | 576.5 |
| 120 | 49 | 622.2 |
| 125 | 52 | 670.4 |
| 130 | 54 | 721.3 |
Normal Operating Pressures
| Condition | Suction (Low Side) | Discharge (High Side) |
|---|---|---|
| Typical summer cooling (95°F OD) | 115-135 PSIG | 380-430 PSIG |
| Mild day cooling (75°F OD) | 105-125 PSIG | 280-330 PSIG |
| Heat pump heating (40°F OD) | 50-75 PSIG | 250-310 PSIG |
Superheat & Subcooling Targets
Fixed Orifice Systems (Piston/Orifice Metering)
Use superheat method for charging. Target superheat varies by outdoor ambient and indoor wet bulb - consult the manufacturer's charging chart on the equipment nameplate or literature.
- Typical target: 10-18°F suction superheat at the indoor coil
- Measure: Suction line temperature (at the outdoor unit service valve) minus suction saturation temperature (from the P/T chart using suction pressure)
TXV/EEV Systems (Thermostatic or Electronic Expansion Valve)
Use subcooling method for charging. Target subcooling is printed on the equipment nameplate (typically 10-15°F).
- Measure: Condensing saturation temperature (from P/T chart using discharge pressure) minus actual liquid line temperature
- If subcooling is below target: system is undercharged - add refrigerant slowly
- If subcooling is above target: system is overcharged - recover refrigerant
High Discharge Pressure Causes
- Dirty condenser coil restricting airflow
- Condenser fan motor not running
- Overcharge - too much refrigerant
- Non-condensables (air/nitrogen) in system
- High ambient temperature
Low Suction Pressure Causes
- Undercharge - low refrigerant (leak)
- Restricted metering device (dirty TXV, plugged orifice)
- Low indoor airflow (dirty filter, bad blower motor)
- Frozen evaporator coil
- Restricted liquid line or filter drier
R-410A Cylinder Handling
- Always use liquid charging on R-410A - it is a zeotrope blend and must be charged as liquid to maintain correct composition
- Invert the cylinder to charge liquid, or use a liquid-line adapter
- Never use R-410A recovery equipment rated for R-22 only
- Store cylinders below 125°F (51°C) - cylinder relief valve opens at 400 PSI